I. Field of the Invention
The present invention relates to a magneto-optical apparatus for writing, reading and erasing information by irradiation with a laser beam on a magneto-optical medium which uses an amorphous material for a recording layer and which is subjected to the writing and erasure of information.
II. Description of the Prior Art
On a magneto-optical medium after writing and reading of information with irradiation of a laser beam, in order to eliminate recording pits in a write pattern by changing the direction of magnetization of the recording layer with irradiation by the laser beam during erasure, the effective beam spot diameter of the laser beam must be larger than that used during the write mode. This is because the pit size becomes larger than the effective beam spot diameter used in the write mode, and the pits cannot be effectively completely erased unless the beam spot during the erasure mode has a larger diameter than that used during the write mode.
However, when the laser beam spot diameter is increased by increasing the laser output, the amorphous material of the recording layer is crystallized which prevents re-recording and reuse of the recording layer.
Furthermore, in a magneto-optical medium which has recording layers formed on the upper and lower surfaces of protective films which are used for two-side recording, when the laser output level is excessively increased so as to erase recording pits on one side during the erasure mode, the recording layer on the other side is adversely affected in prior art devices.